IBM Asks Electrons to the Big Dance

Like planets around the sun, electrons rotate about their axes while orbiting the nucleus of atoms. Spintronic devices generate or manipulate spin-polarized electrons so there are more electrons with one direction of spin. Learning how to manipulate spin is a step toward developing spin-based transistors.

By Richard Adhikari
08/14/12 7:00 AM PT

Researchers from IBM and European university ETH Zurich have announced they have directly mapped the formation of a persistent spin helix in a semiconductor for the first time. They observed how electron spins move in a semiconductor while rotating, like couples doing a waltz. This will let them manipulate the spin, which is a crucial step toward developing spin-based transistors that can be electrically programmed. That, in turn, could help achieve more efficient means of storing data.

"Moore's Law is going to hit a wall in the next 10 years, and spintronics is one of several levers we can pull to continue to produce faster, smaller and more energy-efficient transistors," Chris Sciacca, a spokesperson for IBM Research, told TechNewsWorld.
Researchers from IBM and European university ETH Zurich have announced they have directly mapped the formation of a persistent spin helix in a semiconductor for the first time.

They observed how electron spins move in a semiconductor while rotating, like couples doing a waltz. This will let them manipulate the spin, which is a crucial step toward developing spin-based transistors that can be electrically programmed.

That, in turn, could help achieve more efficient means of storing data.

"Moore's Law is going to hit a wall in the next 10 years, and spintronics is one of several levers we can pull to continue to produce faster, smaller and more energy-efficient transistors," Chris Sciacca, a spokesperson for IBM Research, told TechNewsWorld.

"Given the amount we will have to store in the future, with all of the new big-data and business analytics heading our way, this is an important technology," Joe Clabby, president of Clabby Analytics, told TechNewsWorld. "This is probably why IBM is in the forefront of this technology."

Spin City

As the amount of data we need to store is expanding beyond the capability of traditional storage technologies to handle it, semiconductors continue to shrink through the use of new processes.

That makes it difficult to expand storage capabilities. Data is stored by leveraging the electrical charges of electrons, but as semiconductors shrink, it becomes more difficult to control the flow of electrons.

Spintronics could get around this problem by harnessing the spin of electrons instead of their charge.

Pumping Up the Electrons

Like planets around the sun, electrons rotate about their axes while orbiting the nucleus of atoms. In many materials, there are an equal number of electrons with up and down spins. Spintronic devices generate or manipulate spin-polarized electrons so there are more electrons with one direction of spin.

The length of time the polarized electrons remain that way is known as the "spin lifetime."

The researchers synchronized the electrons in a zinc blende well in a gallium arsenide semiconductor. This synchronization extended the spin lifetime of the electrons by 30 times, to 1.1 nanoseconds. That's the same time it takes for one cycle on a 1 GHz processor, IBM said.

The Techniques Used

The researchers used ultra-short laser pulses to monitor the evolution of thousands of electron spins that were created simultaneously in a very small spot.

This let them see how the spins arranged neatly into a regular stripe-like pattern. This pattern is called the "persistent spin helix."

A carefully engineered spin-orbit interaction coupled the spin with the motion of the electrons. Synchronization of the rotation of the electron spins let the researchers observe the spins travel for more than 10 micrometers. This increases the possibility of using the spin for processing logical operations.

The researchers imaged the synchronous movement of the electron spins with a time-resolved scanning microscope technique.

The project was conducted at 40 Kelvin, which is -387 degrees Fahrenheit.

What's Next

"The next step for the scientists is to improve the spin lifetime even further and to study the materials at higher temperatures," IBM's Sciacca said. The researchers "believe they can bring the temperature considerably closer to room temperature already."

Spintronics "is at the early pregnancy stage," David Hill, principal at Mesabi Group, told TechNewsWorld. "There is a long time before the technology embryo becomes born and even longer before it grows up."

This "kinda reminds me of when processors started to melt down as they approached 5 GHz, which is the end of Moore's Law," Clabby Analytics' Clabby said. "Scientists moved to multi-cores to handle processing in a different way. I'm thinking that some other approach like this multi-core approach would have to be found."

Spintronics will complement, rather than supersede, flash memory, Clabby suggested. "Flash is good for processing high IOPS (Input/Output Operations per Second), but hard drives process other workloads more efficiently. Tapes do storage most cost-effectively. So nothing really supersedes anything else."